Pentyne-3-one

A soln. of l-phenyl-4,4-dimethyl-l-pentyn-3-one in anhydrous dimethyl sulfoxide injected at room temp, during 20 sec. into a stirred soln. of dimethylsulfoxo-nium methylid prepared from trimethylsulfoxonium iodide and NaH in dimethyl sulfoxide, stirring continued 17 hrs. at room temp, and 1.5 hrs. at 70° 1-methyl-3-phenyl-5-rerr-butylthiabenzene 1-oxide. Y 62.8-75.5%. F. e., also isolation of intermediates, s. A. G. Hortmann and R. L. Harris, Am. Soc. 93, 2471 (1971). 

One way to avoid this is to have a mixed copper reagent (2) in which R is preferentially transferred to the cnonc. A good choice for R is an acetylene and the preferred acetylene is 1-pentyne (3) as it is cheap, easy to make, and reasonably volatile. 

Acetylenic alcohols can be converted into ketones in good yield and without side reactions by means of chromic-sulfuric acid in acetone for example, 3-pentyn-2-ol gives 3-pentyn-2-one smoothly at 5-10°.435 Mild oxidation of various steroids and terpenes has been achieved by this procedure.436... 

Oxo-6H derivatives of (12) were obtained from 3-[(4-amino-3-ethoxycarbonyl-6-oxo-l,2-di-hydro-2-pyridyl)imino]-3-ethoxypropionate <83LA753> and 2-[2-(2-pyrimidyl)-2-aryl-l-ethoxy-ethyljmalonates <9iMiP9i 16894, 93MI 823-08). 6-Methylene-2-methyl-6,7,8,9-tetrahydro-4-oxo-4// derivatives of (12) were prepared from 2-(l-pentyn-5-yl)-6-methylpyrimidin-4(3//)-ones <83JHC1407>. 

The photochemical addition of a,jS-acetylenic ketones with alkenes yields acid-sensitive products In the absence of acids, reaction of 3-pentyn-2-one with tetramethylethylene... 

Sensitive ketones such as 3-pentyn-2-one also afford the corresponding vinyl triflate on treatment with Tf20 in the presence of a base (eq 18). ... 

Dimethyl-4-pentynal Oxime, in D-80467 Hexahydro-1 / -pyrrolizin-1 -one, H-60057 Hexahydro-3/ -pyrrolizin-3-one, H-60058 Tetrahydro-1 / -pyrrolizin-2(3//)-one, T-60091... 

Show how the following compounds can be prepared, using ethyne as one of the starting materials. Explain why ethyne should be alkylated before, rather than after, nucleophilic addition, a. l-pentyn-3-ol b. l-phenyl-2-butyn-l-ol c. 2-methyl-3-hexyn-2-ol ... 

The alkane formed by hydrogenation of (S) 4 methyl 1 hexyne is optically active but the one formed by hydrogenation of (S) 3 methyl 1 pentyne is not Explain Would you expect the products of hydrogenation of these two compounds in the presence of Lindlar palladium to be optically active" ... 

The irradiation of 2,5-dimethylfuran in the presence of mercury vapor gave a complex mixture of products. Carbon monoxide and propene were removed as gaseous products. Then, cis- and rran.s-l,3-pentadiene, isoprene, 1,3-dimethylcyclopropene, 2-pentyne, 2-ethyl-5-methylfuran, hexa-3,4-dien-2-one, 1-methyl-3-acetylcyclopropene, and 4-methylcyclopent-2-enone were obtained (Scheme 8) (68JA2720 70JA1824). The most abundantproduct was the cyclopentenone 19, the second was the 1,3-pentadiene 12, while the third product was the cyclopropenyl derivative 18. 

The dinuclear isonitrile and alkoxycarbene complexes 6 and 7 were obtained from [Fe(CO)3( X-dppm) Tl2- j,2-Si(OMe)2(OMe))PtCl] by chloride substitution with isonitriles and 3-butyne-l-ol (or ( )-4-pentyne-2-ol), respectively [2], In these complexes, the organic ligand bound to Pt only occupies one coordination site, thus allowing the trimethoxysilyl ligand to display a T 2- i2-Si-0 bonding mode. 

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